In a typical wireless communication system such as a cellular radio frequency (RF) radiotelephone system, a radio subsystem including a base station system having a controller and a plurality of transmitters and receivers is in communication with a switching center. An interworking unit is often in communication with one or more elements of the radio subsystem. The radio subsystem is responsive to a mobile communication unit, or station, operating within an area served by the base station system.
Multiple access wireless communication between the radio subsystem and the mobile station occurs via RF channels which provide physical paths over which digital communication signals such as voice and data are transmitted. A wireless communication system using code division multiple access (CDMA) channelization is described in detail in standards promulgated by the Electronics Industries Association (EIA) and the Telecommunications Industry Association (TIA), such as TIA/EIA Interim Standard 95 (IS-95), IS-95A and IS-96, each such standard incorporated herein by reference.
To facilitate the wireless transfer of a data communication, many mobile stations are capable of receiving or transmitting digital data from/to computers, facsimile machines and other data sources.
Computers, facsimile machines and other devices associated with other communication systems such as the public switched telephone network may also wish to transfer or receive data communications to/from mobile stations associated with wireless communication systems. one problem encountered when a device desires to transmit a data communication such as a facsimile to a mobile station is an interruption, or dropping altogether, of an RF channel between the mobile station and the radio subsystem. If the RF channel is lost, the calling device would typically have to re-dial the mobile station and re-transmit the data communication, or parts thereof. In addition, the calling device may have to contact the mobile station to determine exactly how much of the data was received prior to interruption of the RF channel.
Although store-and-forward systems exist which allow entire data communications such as facsimiles to be sent by a calling device and retrieved at a later date by a called device such as a mobile station, these systems merely act as mailboxes for data, and the delivery and/or receipt of a particular data communication may be delayed by the use of such systems.
There is therefore a need for a method and system for reliably and in real-time transmitting a data communication to a mobile communication unit, even when a channel over which the data communication is to be transferred is interrupted or is not available.